The present subject matter relates generally to semiconductor fabrication and more specifically to cooling stations used in semiconductor fabrication.
Cooling station lifter pins are currently comprised of ceramic material and may be easily damaged and/or broken thereby deleteriously affecting the performance of the cooling station. When a ceramic lifter pins breaks, it is not uncommon for a robot to crash the wafer, break or scratch the wafer and/or strew particles onto the wafer in a load lock. One such cooling station is the LAM 9600™ Cooling Station manufactured by Brooks which will be used for illustrative purposes hereafter.
FIG. 1 is a perspective view of a portion of a cooling station 10 illustrating three (3) ceramic lifter pins 12 in a V-shaped pattern positioned within a cooling station body 11. The cooling station 10 may be a LAM 9600™ Cooling Station, for example. FIG. 2A is an enlarged portion of FIG. 1 at dashed circle 2 and more clearly illustrates the ceramic lifter pins 12 within the pins' respective sockets 14. FIG. 2B is a further enlarged top plan view of a socket 14 without a pin 12, and FIG. 2C an further enlarged side view of a socket 14 without a pin 12. As more clearly shown in FIGS. 2B and 2C, the socket 14 includes a central opening 15 for the receipt of the pin 12.
One problem with the positioning of ceramic lifter pins within sockets is that a ceramic lifter pin may become separated from its respective socket, resulting in broken ceramic lifter pins.
FIG. 3 illustrates a cooling station 10 operation where a wafer 18 is lifted up by lifter pins (represented by arrows 12) so that a robot (represented by arrow 16) is inserted under the raised wafer 18 to remove wafer 18.
FIG. 4 illustrates a cooling station 10 operation wherein, due to the ceramic composition of the lifter pins 12 or if a robot 16 is not positioned properly, the lifter pins 12 are moved too fast and one or more of the lifter pins 12 may break thereby mispositioning the wafer 18, i.e., not parallel to the robot 16 and/or not positioned above the robot 16. Typically, there is no alarm or other indication of the abnormal operation illustrated by FIG. 4 such that when the robot 16 attempts to extend under the wafer 18, the robot 16 contacts the wafer 18 and possibly breaks the wafer 18.
FIG. 5 is a top plan view of a portion of the cooling station 10 showing the ceramic lifter pins 12 located within openings 24 of a circular platform 20, typically an electrostatic chuck (ESC), in which a wafer is exposed to electricity. As shown in FIG. 5, when the transfer module is pumped down to vacuum, one or more of the current ceramic lifter pins 12 may be unable to maintain a position in the center of the respective openings 24 of the ESC 20. Thus, one or more of the ceramic lifter pins 12 may become positioned very close to one or more of the edges 22 of the openings 24, such that one or more of the ceramic lifter pins 12 may contact the edges 22 of the openings 24 during up and down motion through the ESC 20. Continued friction of the lifter pins 12 against the openings 24 can cause particles from the pin(s) 12 to contaminate the wafer, shorten the life of the lifter pin(s) 12, and cause the pin(s) 12 to break leading to an abnormal cooling station condition as illustrated in FIG. 4.
Accordingly, one or more embodiments of the present subject matter provide an improved lifter pin for cooling stations.
The present subject matter may obviate the deficiencies of the prior art in the following-manner. Specifically, in a cooling station having lifter pins positioned within respective sockets and the lifter pins being positioned for translational movement within platform openings, the improvement wherein the lifter pins are formed of aluminum or polymer. Additionally, a novel cooling station is provided having a cooling station body, a series of sockets affixed to the cooling station body, a respective series of lifter pins comprised of aluminum or polymer affixed to the series of sockets, and a platform positioned on the cooling station body. The platform may have respective openings positioned above the series of sockets and lifter pins for translational movement of the lifter pins into the platform openings.